40HL Measuring System
from GRAS

Typical applications and use

• Measurements at very low sound pressurelevels
• Measurements on hard-disk drives, computerproducts, anechoic rooms, quiet rooms, etc
• Sound-power measurements at low levels

Design

The 40HL comprises a special high-sensitive 1/2″ free-field measurement microphone and an integrated 1/2″ low-noise preamplifier. In combination, they connect to most high-quality input modules with LEMO 1B connector.

Preamplifier

The preamplifier, a true 1/2″ low-noise amplifIer with LEMO 1B connector, has a built-in compensation filter for free-field microphones.

Microphone

The 1/2″ microphone is an externally-polarized free field microphone with a specially reduced inherent noise floor in order to achieve a high dynamic range and wide frequency range. Its diaphragm is specially tuned to yield high sensitivity coupled with low internal noise.